Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A propulsion device including a chamber that stores a superfluid, a
substrate coupled to a portion of the chamber, a plurality of orifices
extending through the substrate, each of the plurality of orifices having
a first end and a second end opposite the first end, the first end
disposed in an interior of the chamber and the second end disposed
outside the chamber; and a pressure source that generates a pressure
differential between the first end of each of the plurality of orifices
and the second end of each of the plurality of orifices.

Claims:

1: A propulsion device comprising: a chamber for storing a superfluid,
the chamber having an outlet; a support mounted in the outlet of the
chamber; a plurality of orifices extending through the support, each of
the orifices having a first end and a second end on an opposite side of
the orifice from the first end, the first end disposed in the interior of
the chamber and the second end disposed outside the chamber; and a
pressure source adapted to generate a pressure differential between the
first ends of the orifices and the second ends of the orifices.

2: The propulsion device according to claim 1, wherein the orifices are
carbon nanotubes.

3: The propulsion device according to claim 1, wherein the chamber is
configured to maintain a temperature of an inside of the chamber below a
critical temperature for superfluidity.

4: A propulsion system comprising: a chamber that stores a superfluid; a
substrate coupled to a portion of the chamber; a plurality of nanotubes
coupled the substrate, each of the plurality of nanotubes having a first
end and a second end opposite the first end, the first end disposed near
an interior of the chamber and the second end disposed near an exterior
of the chamber; and a pressure source that generates a pressure
difference between the first end of each of the plurality of nanotubes
and the second end of each of the plurality of nanotubes.

5: The propulsion system according to claim 4, wherein the chamber is
configured to maintain a temperature of an inside of the chamber below a
critical temperature for superfluidity.

6: A method of propulsion comprising: providing a plurality of orifices
in an outlet of a chamber, the orifices each having a first end located
within the chamber and a second end located outside the chamber;
providing in the chamber a superfluid that has substantially no
viscosity; pressurizing the superfluid within the chamber; and providing
the pressurized superfluid to the first ends of the orifices so that the
superfluid imparts thrust at the second ends of each of the orifices.

7: The method of propulsion according to claim 6, further comprising:
maintaining a temperature of an inside of the chamber below a critical
temperature for superfluidity.

8: The propulsion device according to claim 6, wherein the orifices are
carbon nanotubes.

Description:

TECHNICAL FIELD

[0001] This invention relates to the field of propulsion systems and
methods, more specifically the field of rocket propulsion systems using a
superfluid as a propellant together with orifices provided by nanotubes
to generate thrust.

BACKGROUND

[0002] In the field of propulsion systems that can be used for rockets,
missiles, spacecrafts, and any type of thrust drives, the different
technologies that are currently available for providing the propulsion
can be categorized into different propulsion technology families. The
families that contain most rockets propulsion systems that are in use
today, or planned to be in use in the near future, include chemical
rockets, physical powered rockets, electric propulsion rockets, nuclear
rockets, and laser/ablative propulsion rockets. These families of
propulsion systems have characteristics that are particular to the
family.

[0003] For example, chemical rockets use chemistry to create an exothermic
reaction in the propellant, which causes the propellant to heat up and
expand, generating thrust on a vehicle. This heated propellant, a gas or
plasma, uses the heat released by the reaction to expand. This expansion
pushes against a nozzle attached to the vehicle. This push, acting to
separate the reacted propellant from the vehicle is the mechanism of
momentum transfer, which provides for the motion of the rocket. Chemical
rockets come in many varieties, such as solid rockets, liquid rockets,
hybrid rockets, mono/bipropellant rockets, and others. Chemical rockets
similarly vary widely in complexity, size, and cost. Chemistry is one of
the oldest, and most well understood of the basic sciences behind
propulsion mechanisms. This is one reason why chemical rockets are the
most prevalent of all rockets in use today. The raw materials that
comprise the propellants are also quite abundant. Also, chemical
propulsion systems are noted for their large size, high thrust, and
average specific impulse (Isp). These aspects, coupled with the energy
density of some chemical reactions, allow chemical rockets to provide
comparatively cheap means for generating a large amount of thrust, which
is necessary to launch from Earth or any other potential launching point.

[0004] Physical rockets use the same principle of basic chemical rockets,
i.e., having a propellant pushed out of the rocket by its own energy. The
difference is that the energy does not come from a chemical reaction, but
a physical one. Such reactions include phase changes (liquid to gas) and
pressure changes. These reactions tend to be far less energy dense than
most reactions used by chemical rockets. Physical rockets, however, tend
to have very low thrust, very low Isp, and low efficiencies. For this
reason these rockets are mainly used in model rocketry, and rarely used
commercially.

[0005] Electric propulsion rockets are characterized by powering the
ejection of propellants with a power supply that is kept on the vehicle,
and not, as opposed to chemical rockets, stored in the propellant itself.
To at least some extent, this limits the total momentum transferred to
the rocket by the propellant. As opposed to a chemical rocket, that can
be any size by simply adding more propellant, an electric propulsion
rocket has a maximum amount of propellant it can carry because it has a
limit to the mass of the power supply. Thus, the use of an electric
propulsion system is determined in part by its power supply, not just its
propulsion mechanism.

[0006] Electric propulsion rockets vary wildly in their construction, and
in their operating principles. They do not have to rely on a chemical
reaction for their energy, instead it is often stored in something akin
to a battery, and so, they have the freedom to use this electrical
potential energy in many ways. The complexities of electromagnetism allow
for a large number of possible ways to take an electric potential and use
it to transfer momentum to something. In most cases, electric propulsion
rockets expel low amounts (low mass) of high temperature gases or plasmas
at very high speeds. This results in low thrust and high Isp, both
incomparable to chemical rockets, the first worse, the second better. The
amount of thrust that typical electric propulsion systems can produce is
generally not high enough to be able to launch a rocket from Earth to
orbit, though their high Isps allow for low mass fractions (larger
payload mass and smaller fuel mass) and thus longer term missions. Though
it is not practical to launch this kind of system from the ground, once
in space, this kind of system can be used for correcting satellite
trajectories, deep space missions for probes, and orbit changing. The use
of electric propulsion systems in such situations is quite practical and
even well proven.

[0007] Nuclear rockets have the option to either carry their power in a
battery like device, such as a radioisotope thermoelectric generator, or
other nuclear reactor, or to carry their power in their propellant, by
ejecting small pellets that are to undergo nuclear fission, fusion,
annihilation, or a combination thereof. Essentially, this means that
nuclear rockets may invoke the complexities of chemical or electric
rockets, or both, to cater to a specific goal. As power supplies, nuclear
generators and reactors have the possibility to be hugely more energy
dense than other electric propulsion power supplies, but this is at the
cost of an increased complexity, and the problem of having to deal with
getting rid of the excess heat generated by the nuclear power supplies.
If pellets of nuclear fuel are detonated to deliver thrust, then these
pellets, having reactions with a much higher energy density than chemical
reactions, have the ability to be effective interplanetary engines, and
have enough thrust to launch from Earth. Nuclear rockets in general, have
high Isp and variable thrust to fit the requirement of the application.

[0008] The drawbacks to their implementation are their reasonable
complexity, albeit simpler than many electric rockets, heat management,
safety when using near Earth or in Earth's atmosphere, environmental
issues due to radiation, and animate public concern and distrust. Laser,
ablative, and beamed energy propulsion systems have rarely been
implemented, and have undergone primarily only small scale laboratory
testing. They store their energy somewhere outside of the rocket, beam it
to the rocket, and use it there. How these devices use it varies greatly.
As such, there is no characteristic thrust or Isp for these types of
systems, but what is characteristic is the difficulty in beaming energy
to a rocket. These technologies are still in early research stages. They
are numerous other type of spacecraft propulsion systems and space access
that have been discussed in the literature, but many of these proposals
have one, or more often many, technological problems and, therefore, are
not ready to be implanted in actual flight hardware.

[0009] Regardless of all these existing propulsion system technologies,
for decades the field of high-performance spacecraft propulsion system
research has seen very little beneficial advancement. There is still a
strong need for better propulsion systems.

SUMMARY OF THE INVENTION

[0010] One aspect of the present invention provides a novel propulsion
device and a novel propulsion system. Preferably, the propulsion device
includes a chamber that stores a superfluid; and a substrate coupled to a
portion of the chamber. Moreover, the device further preferably includes
a plurality of orifices extending through the substrate, each of the
plurality of orifices having a first end and a second end on the opposite
end of the tube from the first end, the first end disposed near an
interior of the chamber and the second end disposed near an exterior of
the chamber; and a pressure source that generates a pressure difference
between the first end of each of the plurality of orifices and the second
end of each of the plurality of orifices.

[0011] Another aspect of the present invention provides a novel method of
propulsion. Preferably, the method includes a step of providing a
plurality of nanotubes, and a step of pressurizing a superfluid.
Moreover, the method further preferably includes a step of providing the
pressurized superfluid to a first end of each of the plurality of
nanotubes so that the superfluid imparts thrust at a second end of each
of the plurality of nanotubes.

[0012] The present invention proposes a radically new design for a
propulsion system, for example, but not limited to, rockets, satellite
thrusters, missiles, with many advantages over existing rocket propulsion
technology. The invention takes advantage of several physical effects
that have never before been used in synergy and in the proposed
configuration, to create a novel high efficiency propulsion system
capable of having higher thrust and higher specific impulse. The
invention therefore offers noticeable improvements in terms of
performance. In addition, it uses less toxic or volatile fuel, it has the
potential to open up an entirely new field of spacecraft propulsion
applications and methods.

[0013] The proposed propulsion system solves many problems related to
existing propulsion systems and improves performance and payload mass
fraction. The system is smaller both in mass and in volume as compared to
most existing propulsion systems, and can reduce the cost of launching a
rocket. Thereby the system can also reduce the costs to access to space
or Earth orbit as compared to conventional propulsion system. Also, the
system can reduce the toxicity of rocket exhaust, and at the same time
increases safety, for example as compared to propulsion systems that use
highly volatile chemicals in a combustion process. Moreover, the system
increases the number of possible locations on the surface of the Earth
which can be used for spacecraft launch because the relative efficient
gain of choosing to launch from a location closer to the equator is
lessened.

[0014] The summary of the invention is neither intended nor should it be
construed as being representative of the full extend and scope of the
present invention, in which additional aspects, features and advantages
will become more readily apparent from the detailed description,
particularly when taken together with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other features, aspects and advantages of the present
invention will become better understood with regard to the following
description, appended claims, and accompanying drawings where:

[0016] FIG. 1 depicts a schematic representation of the propulsion system
in a rocket fuselage;

[0017] FIG. 2 depicts a schematic perspective top side view of a matrix of
nanotubes that can be used for the propulsion system;

[0018]FIG. 3 depicts a schematic top plan view of the substrate having a
matrix of nanotubes, in which the substrate is traversed by nanotubes
that can be used for the propulsion system;

[0019] FIG. 4 depicts a schematic top plan view of the substrate having a
matrix of nanotubes with superfluid arranged at the entrance opening
side;

[0020] FIG. 5 depicts a schematic frontal view of the substrate having a
matrix of nanotubes and showing a flow path for the superfluid;

[0021] FIG. 6 depicts a schematic perspective view of the substrate having
a matrix of nanotubes that is traversed by nanotubes;

[0022] FIG. 7 shows a graph that shows physical characteristics of the
superfluid including the temperature and the pressure;

[0023]FIG. 8 shows a schematic representation of a carbon nanotube that
is made of allotropes of carbon with a generally cylindrical
nanostructure;

[0024] FIG. 9 shows a schematic representation of different types of
nanotubes with different wrapping represented by a pair of indices (n,
m);

[0025]FIG. 10 shows a nanoscopic view of a dense arrangement of carbon
nanotubes in a matrix that have been grown by a manufacturing method;

[0026] FIG. 11 shows a schematic representation of a method for
manufacturing the substrate with the nanotubes matrix that can be used
for the propulsion system; and

[0027]FIG. 12 shows a top side perspective view of a matrix of nanotubes.

[0028] Herein, identical reference numerals are used, where possible, to
designate identical elements that are common to the figures. Also, the
images in the drawings are simplified for illustrative purposes and are
not necessarily depicted to scale.

DETAILED DESCRIPTION

[0029] The current state of the art in propulsion systems for rockets and
spacecrafts are limited by the specific impulse and thrust that can be
achieved primary due to specific energy and material property
restrictions. For example, for chemical-reaction based propulsion
systems, in order to increase the specific impulse, one must increase the
temperature of the chemical reaction. This is often limited by the
metallurgical properties of the nozzle such as weight, heat capacity, and
melting temperatures. However, the present propulsion system 100 does not
have these same restrictions because there is no such chemical reaction
that needs high temperatures to achieve any higher Isp.

[0030] FIG. 1 shows a schematic representation of the high specific
impulse superfluid and nanotube propulsion system (HSISNP) 100 in a
rocket fuselage according to the present invention. A sealed chamber 20
is provided in a rocket fuselage 10, the sealed chamber 20 preferably
includes a helium-4 superfluid 25. At one end of the sealed chamber 20 in
a wall of chamber 20, a CNT membrane 30 is provided that includes CNT
matrix 40 having tens or hundreds of billions of vertically aligned
carbon nanotubes 45 arranged thereon, held together by substrate 35. An
entrance side of the CNT matrix 40 is located inside the sealed chamber
20 so that entrance openings 47 of nanotubes 45 are facing the helium-4
superfluid 25, and the exit side is located in the lower fuselage in an
upper area of the thruster 50, so that exit openings 48 of nanotubes 45
are facing the thruster. Each nanotube 45 of the CNT matrix 40 provides a
small channel of nanoscopic dimensions which form small orifices that
allow helium-4 superfluid 25 to pass through from chamber 20 to thruster
50. The flow of helium-4 superfluid 25 from chamber 20 to thruster is
also controlled by superfluid valve system 80 that can shut off any
helium-4 superfluid from passing through CNT matrix. In addition, a power
supply 90 is arranged in the fuselage 10 that is configured to pressurize
chamber 20. Power supply 90 can be configurable and replaceable depending
on the use of fuselage and the mission specs, and can include, but is not
limited to an electric battery, a nuclear reactor, etc.

[0031] The system 100 is not limited to the use of helium-4 superfluid,
other types of superfluids can also be used such as helium-3 superfluid,
or any other yet to be discovered superfluids that exist at suitable
temperatures and pressures that can pass through CNT matrix 40. However,
there are superfluids that are not suitable for system 100, because they
do not exist at usable temperatures or pressures, such as the superfluid
that exists within a neutron star.

[0032] Moreover, chamber 20 is sufficiently thermally isolated that the
fuselage 10 can be fueled up with helium-4 superfluid 25 before the use,
and the critical temperature for helium-4 superfluid is maintained, with
chamber 20 being made of an insulating material, and additional
insulating filler 70 in fuselage. Until the use of helium-4 superfluid 25
is used for propulsion, chamber 20 is not actively cooled for up to a
predetermined period of time. Alternatively, it may be possible that the
chamber 20 is actively cooled by a cooling source (not shown). A
controller 60 that can be configured to communicate with a remote control
station can control the power supply 20 for pressuring the chamber 20,
and the superfluid valve system 80 to open or close the valve so that the
generation of thrust can be controlled. Controller 60 can be equipped
with a timer to activate the power supply 20 and superfluid valve system
at specific precalculated times. Also, controller 60 can be connected to
various sensors measuring pressure in chamber 20, temperature of chamber,
etc. In case a cooling system is present in system 100, the controller 60
could also control the cooling system.

[0033] FIG. 2 shows a perspective schematic view of the nanotubes 45 that
are arranged together as CNT matrix 40, and FIGS. 3-6 show various
perspective and plan schematic views of the CNT matrix 40 with the
nanotubes integrated into a substrate 35. For example, FIG. 2 depicts
twelve nanotubes 45 that are arranged adjacent to each other as a matrix
40, with entrance openings 47 on one side, and exit openings 48 on the
other side. The substrate 35 provides support for the nanotubes. For
representation purposes only, the nanotubes are shown with a length and
diameter of comparable measure. In reality, to maximize Isp, the diameter
of the nanotubes should be minimized, preferably under 10 nm, and the
length is determined by the desired maximum Isp and how axial the
expelled plume of He-II needs to be, for example 100, or 1000 nm.
Moreover, FIG. 4 shows a schematic arrangement of the CNT matrix 40 with
the nanotubes, with exit openings 48 arranged at a thruster side, and
entrance openings 47 arranged in a bath of helium-4 superfluid 25. The
basic operation of the HSISNP system 100 is the use of He-II and the CNT
membrane 30 with their distinct properties in a synergetic effect.
Specifically, a bath of helium-4 superfluid 25, when exposed to no other
exit but a small orifice of a nanotube 45 and subjected to bath pressure
in chamber 20, will "superleak" through the small orifice at a high rate.

[0034] This is because there is very low friction, or more accurately an
analogue to friction, within the helium-4 superfluid 25 and between it
any structure it is in contact with. In conventional fluid-dynamics, the
smaller the orifice the fluid is forced through, the larger the effect of
friction and, thus the larger the inefficiencies of that movement.
However, with superfluid materials, there is an unexpected result that
the smaller an orifice or a hole that a superfluid is forced though, the
more efficiently the superfluid moves though that orifice or hole. Due to
this severe lack of friction associated with helium-4 superfluid 25, it
is possible to push superfluid 25 through very small holes, such as the
orifices of the nanotubes 45, with a very high efficiency. Superfluidity
is a property that some collections of particles can achieve at certain
extreme conditions such as extreme low temperatures. The characteristic
of superfluidity of importance to the present invention is the lack of
any measurable viscosity and surface friction. There are however, many
other properties of superfluids that result, such as, the thermomechanic
effect, the mechanocaloric effect, the Josephson Effect, and the
existence of quantized vortices, a Rollin film, etc., all of these
properties being manifested at the full range of the superfluid phase,
which for helium-4 superfluid is below a critical temperature of
˜2.17K. None of these will greatly affect the system except the
existence of quantized vortices.

[0035] The properties of helium-4 superfluid 25 specifically dictate that
its flow rate be governed by many variables, such as, temperature,
pressure differential across the orifice from the chamber 20 to upper
area of thruster 50, orifice geometry, orifice material, orifice depth,
initial condition of the bath of the helium-4 superfluid 25, including
any initial turbulences, impurities, and wave propagations, and exposure
to outside forces and energy such as, but not limited to, light, heat,
sound, vibrations. These variables determine the equations governing the
flow rate both below and above a critical velocity, and what the critical
velocity is.

[0037] FIG. 7 shows a graph representing a phase diagram of helium-4,
illustrating the temperatures and pressures in which it is known to
exist. For the present HSISNP system 100, helium-4 superfluid 25 can be
used due to its specific physical properties. Helium-4 superfluid 25 is
formed at critical temperatures at least hundreds of times hotter, at
about ˜2.17 K than other known or theorized superfluids such as
helium-3 superfluid that has a critical temperature of 2.49 mK, and is,
therefore, far easier to create and to maintain cooled than most other
superfluids with insulation elements 70, 95. It is therefore possible
that insulation elements 70, 95 can maintain the sealed container 20
below the critical temperature more easily when using the helium-4
superfluid 25.

[0038] Moreover, properties of helium-4 superfluid 25 include zero
viscosity below a critical velocity, quantized flow defects above a
critical velocity, critical velocities that are container dependent, very
high thermal conductivity that varies with temperature, the transfer of
nearly all or even all energy as quantized waves, the existence of a
Rollin film that creeps over all surfaces to find a lower energy state,
odd specific heat curves, quantized microscopic movement, such as in
quantized vortices, vibrations, flow, etc., the mechanocaloric and
thermomechanic effects, which translate movement with heat, and the
Fountain Effect. In the proposed HSISNP system 100, what is of primary
importance are those properties relating to fluid flow and critical
velocities, though some other properties of helium-4 superfluid 25 have
to be taken into account also. Carbon nanotubes are particularly suitable
since they have smooth surfaces and form a cylindrical orifice, minimized
orifice diameter, and can be manufactured to an optimized orifice length.

[0039]FIG. 8 shows a schematic representation of a carbon nanotube that
is made of allotropes of carbon with a generally or substantially
cylindrical nanostructure, and FIG. 9 shows a schematic representation of
different types of nanotubes with different carbon tube wrapping, wherein
the carbon structure is shown defined by pairs of indices (n, m). One
important aspect of the present invention is the use of the CNT membrane
30 for the HSISNP system having CNT matrix 40 of nanotubes 45. CNT
nanotubes 45 in the matrix are allotropes of carbon with a cylindrical
nanostructure. Nanotubes 45 are members of the fullerene structural
family, and can be formed with a length-to-diameter ratio of up to
132,000,000:1. Also, the walls of nanotubes 45 are preferably formed by
one-atom-thick sheets of carbon. These tubes 45 may or may not be capped,
have splits, junctions, and different bonding layouts, but like
fullerenes, are all one molecule. They have very high strengths,
especially tensile strength, higher than any other known material, high
oscillation frequencies, and high thermal and electrical conductivity
along their length.

[0040] The helium-4 superfluid 25, when forced through the nanotube matrix
discussed above, results in an easily accelerated fluid that can achieve
speeds fast enough to be useful as part of a rocket propulsion system. By
using the accelerated superfluid as the propellant, or as an expelled
mass, of a rocket, it is possible to achieve specific impulses that are
higher than the upper limit of chemical propulsion technology, with a
very high maximum specific impulse. Also, it is possible to
simultaneously expel an amount of superfluid that is at a mass flow rate
comparable to chemical rocket engines. As such, the HSISNP system 100
described above has a greater specific impulse than most or all chemical
rockets, and a greater mass flow rate, and thus thrust, than other high
specific impulse alternatives such as electric propulsion.

[0041]FIG. 10 depicts a microscopic representation of dense nanotubes 45
in an array produced from a Fe-catalyzed chemical vapor deposition
process. A method of manufacturing the CNT membrane 30 is illustrated in
an exemplary embodiment in FIG. 11. In this method, membrane 30 consists
of CNT nanotubes 45 arranged in parallel at a density of about 60
billion/cm2 traversing a polymer film, having a length of about 5
μm. The CNT nanotubes 45 are grown by a chemical vapor deposition
process (CVD). Next, the nanotubes are spin-coated using a polymer, for
example polystyrene (PS) and Toluene, to form substrate 30, and the
excess polymer is removed from the top surface. Then the quartz substrate
is removed using Hydrofluoric (HF) acid. Finally, a thin layer of excess
polymer is removed by a plasma etching process. Such exemplary method of
manufacturing a nanotubes membrane is described in the publication
entitled "Nanotube Membranes: Super Fast Flow in Very Small Pipes,
Energeia," Rodney Andrews, Bruce Hinds, Vol. 17, No. 2, 2006, Center for
Applied Energy Research (CAER), University of Kentucky, this reference
being incorporated by in its entirely by reference. This method of
producing CNT membranes 30 is only provided as an example, but many other
methods of producing the CNT membrane 30 may be used. Also, the encasing
material does not have to be polystyrene, other materials can be used
that are more suitable for the application.

[0042] To create a propulsion system 100 using the carbon nanotubes
described above and with superfluids as a propellant, a completely sealed
chamber 20 is employed that is filled with helium-4 superfluid 25 and
operated at or below a critical temperature of 2.17 K. 2.17 K is the
approximate temperature at which liquid helium becomes or behaves as
superfluid helium, as shown in FIG. 7. It must be noted that when dealing
with any sort of container intended to store superfluid helium, the
container must be completely sealed. That is to say that the container
must not have any holes or any other material defects, including in any
gaskets, flanges or seals, that penetrate through the container wall with
a defect entrance diameter larger than a few hydrogen atom diameters.
This is due to the fact that the superfluid will leak though any hole
larger than the healing length of helium. In light of helium-4
superfluid's 25 ability to superleak, the proposed propulsion system 100
requires a specialized sealed chamber 20 to store and manipulate helium-4
superfluid 25 to avoid any stray leaks.

[0043] The CNT membrane 30 with the CNT matrix 40 is located in the outlet
of the sealed chamber 20. As discussed above, the CNT matrix 40 is
composed of tens to hundreds of billions of preferably substantially
vertically aligned single wall carbon nanotubes 45. The vertical and
parallel alignment, with preferably substantially the same diameter and
length, results in the tubes being oriented in substantially the same
direction as shown in FIG. 12. Such an arrangement provides an efficient
propulsion force out of the chamber. As discussed above, the carbon
nanotubes are supported in a solid substrate composed of polymer material
that is able withstand the propulsive forces generated during use, while
maintaining the position of the nanotubes. The polymer also acts as an
insulator for the nanotubes and a seal for the chamber opening. While a
polymer has been discussed above, the material can also be metal, ceramic
or an organic compound. The substrate 30 needs to be built to withhold
forces, and the force that will need to be withstood by the membrane 30
will be inversely proportional to the frictional losses in the membrane
30 from transferring energy from the power supply 90 to the helium-4
superfluid 25.

[0044] In order to permit flow through the tubes, the CNT membrane 30 must
not cover or obstruct either openings 47 and 48. Instead, it is
envisioned in one embodiment that the substrate 35 encases the carbon
nanotubes half way between the carbon nanotubes top and bottom, as shown
in FIGS. 3-4. In another embodiment, the membrane 30 is a flat plate with
a matrix of holes in it, the matrix of holes being configured to hold
individual carbon nanotubes 45. These holes have a diameter that is just
ever so slightly larger than the diameter of the carbon nanotubes.
Alternately, the holes may each be large enough to hold multiple
nanotubes.

[0045] The substrate 35 holding the CNT matrix 40 is attached to the wall
of the sealed chamber 20 in any one of numerous ways, including, but not
to, through the use of adhesives, physical obstructions (e.g., flanges),
clamps, magnets, etc. Once the CNT matrix 40 is securely in place, a
vacuum 55 may be establishes on the side of the CNT matrix 40 opposite of
the sealed chamber 20. The purpose of this vacuum 55 is primarily to
provide a physical property which results in the propulsion system having
the same specific impulse regardless of its altitude and the
environmental pressure. The vacuum 55 also serves to thermally isolate
any potential comparatively hot atmosphere the propulsion system 100 may
be in from the exit openings 48, which must be kept as cold as the
superfluid 25. The power supply 90 is primarily used to pressurize
chamber 20 to cause there to be a sufficient pressure differential or
gradient to push the superfluid out of the chamber at a high speed. The
vacuum 55 at the exit openings 48 can be created through the use of a
mechanical vacuum pump (not shown) which is incorporated into the
propulsion system 100 itself. When outer space, the ambient vacuum is
sufficient to act as the vacuum 55, and no additional vacuum needs to be
artificially generated. The vacuum 55 can be artificially generated, for
example by incorporating channels or ducts 75 downstream from the exit
openings 48. Moreover, ducts 75 can also be equipped with a fan or
turbine 78 to accelerate the air flow through ducts 75 to further reduce
the pressure. Vacuum pumps that are inside the fuselage could also be
used (not shown). The channels 75 would produce an effect during
atmospheric flight as air moves over the external surface of the rocket
fuselage 10. The aerodynamic flow will create a low pressure area at the
exit openings, aiding the vacuum pump in generating the vacuum 55.

[0046] As explained above, in order to accelerate helium-4 superfluid 25
through the nanotubes 45 themselves, a pressure differential or gradient
must be established between entrance openings 47 and the exit opening 48
of the carbon nanotubes 45. The formation of the vacuum or low pressure
zone on the downstream side of the nanotube matrix provides part of
pressure differential. However, most of the pressure gradient originates
from the pressurized helium-4 superfluid 25 by the application of
pressure to the sealed chamber through the power source 90.

[0047] Considering the existence of this pressure gradient and the fact
that there is a vacuum 55 on the exit side of the carbon nanotubes 45 and
the inherent nature of superfluid to move though tiny holes and cavities
with extreme ease, the superfluid in the sealed chamber 20 of the
propulsion system will leave the chamber 20 the only way that it can,
through the nanotubes 45 of CNT matrix 40. The empirical data regarding
superfluids ease of movement though small capillaries coupled with the
internal fluid flow properties of nanotubes 45 and the pressure
differential, will result in the helium-4 superfluid 25 moving though
carbon nanotubes 45, and exit openings 48 of nanotubes 45 with a very
high exit velocity. Testing of fluid flow through carbon nanotubes by the
University of Kentucky has shown volumetric flow rates that are, when
exposed to a specific pressure differential, four to five orders of
magnitude higher than expected using standard fluid dynamic theory. With
carbon nanotube lengths of about 5 μm, 6-10 nm of inner diameter, end
flow rates of up to 44 cm/s have been generated.

[0048] Calculation based on extrapolations of empirical data of He-II
moving through holes of similar geometry as the diameters of the carbon
nanotubes 45 according to the present invention indicate this velocity to
be approximately 16,170 m/s, which equals a specific impulse of 1,650
seconds ((16,170 m/s)/(9.8 m/s2)=1,650 s). This calculation does not take
into account the potential performance gained by using CNTs. By
incorporating CNTs, as compared to the holes of similar dimensions, it is
expected that the result will be higher, possibly four to five orders of
magnitude higher as found with all other fluids. Most spacecraft
propulsion systems that have an operating specific impulse that is on the
order of 1,650 seconds are either electric propulsion systems, which do
not create much thrust, or nuclear propulsion systems, which do have high
thrust but they also very costly and may be problematic for the
environment. One reason why traditional nuclear propulsion system
concepts are not in common use is that most nuclear propulsion system
concepts, either deliberately or though side effects of design and
engineering, expel large amount of radioactive material as momentum
transfer mass.

[0049] The present HSISNP system 100 presents substantial advantages over
the existing propulsion system. For example, the system 100 is neither
limited to the low thrust regime nor does it expel radioactive material
even if it where powered with a nuclear power source. One of the reasons
the system 100 can have such high performance is the large number of
physical properties which, when studied either on a case by case basis or
on a system wide level, turn out to be extremely efficient when operated
in conjunction. For example, superfluids have no internal viscosity, and
experience virtually no friction when they leak though small holes or
capillaries. Superfluids move though small holes more easily the smaller
the hole is, until the holes diameter is a few hydrogen atom diameters
across. This is an unexpected result when looking at conventional
fluid-dynamics. Moreover, carbon nanotubes 45 have extremely low internal
friction, liquids moving though carbon nanotubes move up to five orders
of magnitude faster than traditional fluid mechanic calculations would
indicate. Hie critical velocities are increased with the smoother the
orifice is. Therefore, the propulsion system 100 has the potential to be
unrivaled in terms of total systematic efficiency in converting a
potential energy into a propulsion force.

[0050] Moreover, the HSISNP system 100, and its integration into a
fuselage or spacecraft, can provide substantial advantages over the
pre-existing propulsion solutions. In use, a spacecraft would be equipped
with a suitable charged power supply for providing the pressure needed. A
sealed chamber 20 in the fuselage is filled with helium-4 superfluid. The
spacecraft can safely sit on a runway awaiting launch. Next, a computer
located at a base station sends a signal controller 60 to start using the
power supply 90 to pressurize the chamber 20. As the pressure builds
within the chamber, pressured helium-4 superfluid can be allowed to be
released though the CNT matrix 40 to generate thrust. At this time, the
controller 60 can control the superfluid valve system 80 to allow flow of
superfluid 25 through the CNT matrix 40. As superfluid 25 is ejected out
of the propulsion system 100 through the thruster 50, a thrust force is
generated. This thrust and total duration of propulsion is sufficient to
cause the spacecraft to reach low Earth orbit in a single stage. While on
a mission the superfluid 25 probably can be kept at the critical
temperature 2.17 K or below with an appropriate combination of insulation
70, 95 and also a cooling system for the duration of the mission.

[0051] Based on the estimations, it is possible that a spacecraft that is
equipped with the propulsion system 100 can reenter the Earth's
atmosphere without the need to use a heat shield. Generally, there is no
inherent need for reentering spacecraft to have a heat shield. Heat
shields are used solely to bleed off the enormous kinetic energy that a
spacecraft in Earth's orbit needs in order to sustain orbit. Effectively,
current spacecraft use their rocket engines to accelerate from 0 kph to
orbital velocity of 36,000 kph and then run out of fuel. When it is time
to return to Earth, the spacecraft use aerodynamic effects between
Earth's atmosphere and the spacecraft's heat shield to convert the
enormous kinetic energy of orbital velocity into heat that is dissipated
and dispersed throughout the atmosphere. The avoidance of a heat shield
will reduce your payload mass fraction. With a high performance
spacecraft propulsion system, such as the one proposed herewith, the
spacecraft can use its rocket engines while in orbit to nullify its
orbital velocity so that it can fly back to the spaceport in a more
controlled manner. As stated previously, the superfluid 20 that is
proposed as a propellant for the HSISNP system 100 is not an energy
source. In order to use it as a propellant, it must be supplied with
energy through some other means. This is part of the reason that the
HSISNP system 100 can span such a large range of specific impulses and
thrust, which fundamental parameters will depend on the type of power
supply 90 that is used in the system. In general the most important
parameter for a power supply 90 is the energy density per mass of the
power supply 90, including reactant masses and structural requirements.
There are a number of options for powering the proposed propulsion system
100. For example one could use a standard exothermic reaction to power a
turbine and energize (pressurize) the superfluid propellant.

[0052] Some chemical compositions that could produce this exothermic
reaction are, but are not limited to, liquid Hydrogen and liquid Oxygen,
Lithium and Fluorine (preferably solid), Kerosene and Oxygen, Iron Oxide
and Aluminum (Thermite), Aluminum and Oxygen, Magnesium and Oxygen,
Hydrogen Peroxide dissociation, Hydrazine dissociation, Nitrous Oxide and
Rubber, and Aluminum Perchlorate Composite Propellant. As these are all
chemical reactions, they all have comparable energy densities
(˜3-40 MJ/kg), so choosing one reaction over another would likely
be predicated on other secondary factors. Another possible chemical power
supply that could be used would be an air breathing hydrogen engine, this
would have a higher than average energy density (˜b 143 MJ/kg) for
a chemical power plant. Such a power plant would not require the storage
of an oxidizer. An air breathing chemical power supply is believed to be
the upper limit of energy densities that can be obtained via chemical
reactions and carries with it some well understood engineering
limitations. Such power supply should be thermally isolated from the
sealed chamber.

[0053] The previously listed power supply sources all rely on
electromagnetic force interactions, another category of power supplies
would be those which use strong force reactions. Strong force intentions
are inherently more energy dense than electromagnetic force interactions
and, therefore, have the potential to be beneficial in the present
invention. A variety of nuclear reactors could be used as a power supply
90. These include standard Uranium 238 fission, light water reactors, and
fast breeder reactors. Some less standard nuclear reactors could also be
considered: Thorium cycle fission, and Uranium-Zirconium-Hydride fission
(TRIGA). These two examples are unique in that they enjoy a negative
temperature reaction coefficient, meaning that it is physically
impossible for them to meltdown in the traditional sense. These options
have energy densities ranging from 10,000,000 to 100,000,000 MJ/kg.
Another strong force option is Induced Gamma Emission where nuclear
isomers store energy in specific excitation states, this can be done
relatively safely with about 5 nuclear isomers boasting energy densities
as high as 1,000,000 MJ/kg. This is a useful energy density and, since
Induced Gamma Emissions does not involve the creation of radioisotopes,
is, therefore, generally safer than most other strong force interactions.
All in all choosing a power source 90 is highly dependent upon the
specific use of the propulsion system 100.

[0054] The advantages of the HSISNP system 100 over the existing
propulsion systems are many, as already discussed in some detail above.
One significant feature of the propulsion system 100 is that it uses He
as the propellant, while most existing propulsion systems use highly
volatile chemicals in a combustion process. In addition, the byproduct of
the propulsion system is He which is a noble gas and, therefore,
non-toxic, environmentally friendly, non-corrosive, not a greenhouse gas,
and non-combustible. In addition, the chamber 20, which is filled with
liquid He, is inherently safer compared to propulsion systems that use
traditional chemical explosion. In other words, since He is an inert gas,
the present invention generally will not be susceptible to exploding via
an exothermic chemical reaction. Another way to explain this is to say
that liquid He likes the state it is in, and it will not phase change or
otherwise chemically react besides through normal thermal evaporation
which is a generally much less energetic process.

[0055] Another advantage of propulsion system 100 is that it uses a
subsystem of liquid He pressurization and storage devices and a nozzle
like subsystem, both of which are small in mass and volume. The decrease
in the size, mass, and volume of the propulsion system 100 can reduce the
size, mass and volume of the fuselage 10 and the space vehicles
themselves. As should be apparent, generally small spacecrafts cost less.
Also, the He based superfluid is easy to transport, store, and is
relatively inexpensive as compared to other propellants.

[0056] Still another advantage of the propulsion system 100 is that, as
discussed above, it has a high specific impulse (high fuel efficiency
performance). This means that a launch vehicle using our superfluid
propulsion system can send more payload mass to a destination while at
the same time using less propellant than current rocket systems. The
advantage will reduce the cost of access to space and increase the market
share using the propulsion system. One reason why the system 100 has a
high specific impulse is that superfluid helium and other superfluids
have, by definition, no internal viscosity (under certain conditions).
This means that when superfluids flow through or around physical objects
or obstructions, the superfluid does not slow down due to viscous drag.
Therefore, when the system 100 forces superfluid helium through very
small holes, the superfluid will be accelerated without much, if any,
efficiency losses.

[0057] The superfluid expelled is naturally collimated, as such, using
vector mechanics, it can be established that the collimated stream
imparts substantially all of its momentum exactly in the desired vector
or direction. Such a well-directed propulsive stream out of a thruster 50
is not at all common in the existing propulsion systems where the vast
majority suffer some noticeable thrust vector propulsion efficiency loss.

[0058] Another reason the propulsion system 100 has a high specific
impulse is that the ejected superfluid helium is around 2 degrees Kelvin.
As such, the ejected fluid has very little internal energy, other than
its quite large kinetic energy. This lack of inefficiently-used internal
energy, in turn, means that the ejected working fluid does not have any
tendency to adiabatically expand. The lack of adiabatic expansion
simplifies the thermal engineering analysis and decreases thrust losses
due to vector mechanics effects that are epiphenomena of adiabatic
expansion.

[0059] Still another reason why the propulsion system 100 has a high
specific impulse is that carbon nanotubes 45 have a property of extremely
efficient internal fluid transfer. Another advantage of the propulsion
system 100 over existing electric propulsion systems is that it does not
eject charged particles. The ejection of charged particles is
disadvantageous since, unless it is counteracted, the expelled charged
particles can change the electric charge of the spacecraft itself.
Moreover, the use of super-cold superfluid He combined with the use of
carbon nanotubes 45, results in relatively little frozen flow.

[0060] Yet another advantage of the propulsion system 100 is that through
the use of carbon nanotubes 45, the superfluid propellant can be forced
though otherwise unattainably small holes. Due to a higher critical
velocity of superfluity when the superfluid traverses a hole or orifice
of a very small diameter, the superfluid moves more efficiently through
that hole. This fact adds to the overall efficiency and specific impulse
of the propulsion system 100.

[0061] Still another advantage of the propulsion system 100 is that the
nozzle, as compared with chemical propulsion systems, is composed of
carbon nanotubes which are extremely strong, and relatively inexpensive
to grow. Yet another advantage is that if an engineer chooses to use a
nuclear reactor as a power source 90, the exhaust stream would not be
radioactive.

[0062] Yet another advantage of the propulsion system 100 is that it can
be restarted, effectively, an infinite number of times, without the need
to wait for more optimal operating temperature for the chemical
reactions. Existing chemical reaction based propulsion systems cannot be
restarted; some like the J-2 liquid-fuel cryogenic rocket engine used on
NASA's Saturn IB and Saturn V launch vehicles can only be restarted every
90 minutes, or it may be possible to attempt a restart after 35 minutes
if the operator wants to risk an explosion. The present invention does
not require this much time to restart, and the restart time is not
inherent in the superfluid; it depends on the power supply, the valves,
etc., all of which are interchangeable.

[0063] Still another advantage of the propulsion system 100 is that it has
both a sufficiently high thrust and high specific impulse so that it is
possible for an aircraft that is equipped with system 100 to avoid the
need of a heat shield for reentry. This is possible because, if a
spacecraft has an advanced high-performance rocket engine then the
spacecraft can use its rocket engine to decelerate instead of using the
aerodynamic effects of a traditional heat shield moving though the
atmosphere. Yet another advantage of the proposed propulsion system 100
is that there is no need for multiple propulsion stages, thus reducing
the weight of the vehicle, and permitting a more efficient flight
trajectory. In other words, system 100 has sufficient power, thrust, and
specific impulse to allow for the construction of single-stage-to-orbit
vehicles that are fully reusable. Such a single-stage-to-orbit vehicles
should be less expensive to operate than traditional multi-stage
expendable rockets, or partially reusable spacecrafts such as NASA's
Space Shuttle. Another advantage of the proposed propulsion system 100 is
that its performance versus cost ratio can be sufficiently economical to
allow for traditional high-performance jet planes, such as corporate
jets, supersonic transports, military assets, to use the proposed
propulsion system 100 as a thrust source, instead of traditional
turbines. The proposed system 100 could also well be used for propelling
other vehicles and devices.

[0064] Another advantage of the propulsion system 100 is that its specific
impulse, unlike most current technology, does not reduce with decreased
atmospheric altitude. In other words, for most existing propulsion
systems, the specific impulse increases at high atmospheric pressure, for
example at lower altitudes, and use nozzles which are engineered to
perform at maximum efficiency only at a certain altitude or atmospheric
pressure. As an example, consider the Space Shuttle Main Engine's
performance (SSME) data. The SSME produces 2,278,824 Newton's of thrust
at a specific impulse of 452 seconds while in a vacuum, and a thrust of
1,859,357 Newton's of thrust at a specific impulse of 366 seconds while
at sea level. Considering what is available in existing propulsion
systems, it is advantageous that the propulsion system 100 has a specific
impulse in a vacuum Isp (vac) that is always the same regardless of the
environmental pressure. The reference to the specific impulse Isp in
vacuum is based on the assumption that propulsion system 100 is thrusting
into a vacuum at all times. The motivation for operating propulsion
system 100 in vacuum is to thermally insulate the very cold helium-4
superfluid 25 from the local environment, and a useful side effect is
that we are always thrusting into a vacuum. Because we are always
thrusting into a vacuum, the local external (atmospheric) pressure does
not matter and our performance therefore not be changed by different
pressures at different altitudes.

[0065] Another advantage of the propulsion system 100 is that a reusable
spacecraft that uses it can be easily, quickly, safely, and relatively
inexpensively refueled. This property makes this propulsion system 100
very attractive to commercial spaceflight launch, space tourism launch
providers, as well as other organizations and individuals.

[0066] Although the invention herein has been described with reference to
particular embodiments, it is to be understood that these embodiments are
merely illustrative of the principles and applications of the present
invention. It is therefore to be understood that numerous modifications
may be made to the illustrative embodiments and that other arrangements
may be devised without departing from the spirit and scope of the present
invention as defined by the appended claims.

Patent applications by Joseph D. Nix, Fort Wayne, IN US

Patent applications by Michael Wallace Verhulst, Springfield, IL US

Patent applications by BOARD OF TRUSTEES OF NORTHERN ILLINOIS UNIVERSITY